For Windows XP, Server 2003, and Vista, this will only work for data (Non C:\) partitions. It will work for all disks on Windows 7, 8, 2008/R2, 2012/R2 disks (including C:\).

NOTE: Be cautious, you can grow disks as many times as you want (up to 2TB) but not shrink them (in Vista, 7/8, 2008/R2, 2012/R2 you can shrink the partition but cannot shrink the underlying disk).

1. Allocate additional free disk space on the Disk

For VMs, you first must increase the VMs disk size using VMware vSphere client or Hyper-V Host server. Find the VM that you want to expand, edit the properties of its virtual disk to increase it. (see Adding/Editing VMware Virtual Disk)

For physical servers, move/remove partitions as needed

2. Confirm New Space

Back to the computer, right-click My Computer > Manage. Go to Disk Management, right-click and Re-Scan Disks if it hasn’t already shown the new extent. Confirm the new space is available on the same disk as the partition you want to extend.

3. Use DiskPart to Extend

Open command prompt as Administrator and perform the following:

>diskpart

>list volume

>select volume VOLUME_#_TO_BE_EXTENDED

To extend using all available space:

>extend

To use a portion of the available space

>extend size=SIZE_IN_MB_THE_PARTITION_SHOULD_BE_EXTENDED

If the partition still shows the same amount of free space it had prior to being extended, go back to >diskpart, select the volume and try:

3. You can see the existing virtual disks in the hardware list. Once highlighted, you can adjust the size of the VD. You can also see the disk type, the disks datastore location, and name of the actual VMDK file. From this screen you can also select Add… to add a new virtual disk: